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This is an editorial paper focusing on emerging topics in joint wireless positioning, sensing, and communications. After introducing the sometimes-confusing and non-unified terminology in the field and defining the overall research area under the comprehensive terminology of Joint positioning, sensing, and communications (JPSAC), a brief state-of-the art overview is given, followed by a detailed list of emerging topics and open research questions. The ongoing Horizon Europe projects are also reviewed in relation to the emerging JPSAC. Some of the main trends in the JPSAC-related areas are related to extremely large-scale antennas and apertures, reconfigurable intelligent surfaces, the integration of terrestrial and satellite-based communication, sensing, and positioning functionalities, and cell-free or distributed networks with JPSAC functions. [ABSTRACT FROM AUTHOR]

A novel common-aperture miniaturized antenna with wideband and dual-polarized characteristics is proposed, which consists of a circularly polarized (CP) and a linearly polarized (LP) antenna. The circularly polarized antenna stacked on the upper layer adopts asymmetrical ground and introduces the patch and T-type feed network. On this basis, the meshed reflector structure, which also works as a ground plane for the LP antenna, is added to reduce the influence on circular polarization and achieve directional radiation. The LP antenna stacked in the lower layer uses a monopole structure, and the coaxial feed line perforates the reflector, and thereby the common-aperture antennas are tightly stacked together from top to bottom. Simulation and test are in good accordance, and the results show that the two ports of the antenna are well matched in the range of 5.5 GHz to 7.8 GHz, where peak gains of 8.5 dB and 6 dB are realized for circular polarization and linear polarization, respectively. Moreover, the 3 dB axial ratio (AR) bandwidth of the CP antenna is 34.3% and the isolation between the two ports is better than 15 dB, suggesting potential applications in the relay platform or drone detection for signal transmission and reception. [ABSTRACT FROM AUTHOR]

A novel broadband dual‐polarised transmitarray antenna (TA) utilising tightly coupled cross dipole cells is proposed in this work. The transmitarray cell using the tightly coupling wideband principle comprises two radiation patches designed as two orthogonal planar dipoles with four interdigital capacitors, two meandered parallel plate transmission lines, and a ground. Each cell has a square shape and a dimension of approximately 0.28 λc ${\lambda }_{\mathrm{c}}$ where λc ${\lambda }_{\mathrm{c}}$ is the wavelength at central frequency 5.5 GHz. The transmitarray cell can achieve 475° phase shift at central frequency and transmission magnitude better than −2.5 dB within the working band. To verify the feasibility of this design, a tightly coupled dual‐polarised transmitarray antenna (TCDPTA) is modelled and manufactured. The transmitarray aperture size is approximately 4.1 λc ${\lambda }_{\mathrm{c}}$× ${\times} $ 4.1 λc ${\lambda }_{\mathrm{c}}$. The simulation and measurement illustrate that the TCDPTA has stable and distortion‐free main beams whose side lobe levels are generally below −10 dB in the band of 3.0–8.0 GHz. The measured gain at central frequency is 16.2 dBi and peak gain is 19 dBi at 7.5 GHz. The working bandwidth is 90.9% and 3 dB gain bandwidth is 66.7%. The measured cross‐polarisation levels are below −15 dB at axial direction. This TA has potential applications for high‐date‐rate communication and high‐revolution radar imaging systems at C‐band. [ABSTRACT FROM AUTHOR]

To achieve multi‐function integration and independent performance regulation of microwave and millimetre‐wave (mm‐Wave) shared‐aperture antennas, a design method based on embedded structure fusion is proposed. In the Sub‐6G band, a high‐order mode annular‐ring patch antenna is designed. To transform the non‐broadside characteristics, the current distribution of TM31 and TM12 modes is reconstructed by slotting in the centre of the patch. Additionally, the electric field distribution is modified by loading shorting pins to achieve beam broadening. In the 5G mm‐Wave band, a four‐element high‐gain substrate integrated waveguide (SIW) slotted cavity backed antenna array with low‐sidelobe characteristics is obtained using the element interleaving technique. The SIW slotted cavity backed antenna array is integrated into the central area of the annular‐ring patch to achieve aperture‐sharing fusion. Experimental results demonstrate that the antenna operates in the Sub‐6G dual‐band of 2.1–2.2 GHz and 5.2–5.4 GHz, respectively. Furthermore, the widest half‐power beamwidth measured in these two bands is 126° and 140°. In the mm‐Wave band, the operating bandwidth is 26.5–29.5 GHz, with a gain of up to 18.8 dBi. Notably, the performance of different bands does not impact the other, and the measured isolation exceeds 40 dB. Furthermore, the antenna profile is only 0.008 λ0. Therefore, an ultra‐low‐profile microwave and mm‐Wave shared‐aperture antenna with multi‐function integration and independent performance control is realised, which has great potential for application in 5G intelligent connected vehicle communications. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) can collect earth surface information with synthetic aperture radar (SAR) sensors during night, day, and bad weather. However, UAVs have only limited volume and weight for the SAR payload. A very light dual circularly polarized pyramid horn antenna was developed in order to improve sense capability in UAV dual polarimetry SAR images. The pyramid horn was designed and simulated in computer simulation technology (CST) 2022. The horn was capable of producing two circular polarizations right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) alternately using a three stepped septum polarizer and coaxial probe feed on two sides of the waveguide. The results show that the horn antenna was capable of having a wide S11 and S22 bandwidth from 4 GHz to 6.7 GHz. The horn was capable of producing two circular polarizations with an axial ratio below 3 dB from 4.4 GHz to 6.4 GHz. This gain horn antenna was relatively stable in the range of 15 dBiC with a reasonably narrow 3 dB beamwidth of 28° both RHCP and LHCP polarisation in E and H fields respectively. [ABSTRACT FROM AUTHOR]

Unlike popular multiband antenna array radiation based on either electric or magnetic surface currents, the use of mutually interleaved and tightly coupled electric and magnetic currents results in an aperture-reuse space-efficient multiband radiating surface for highly integrated antenna-frontend architecture and spatial power combining design scenarios. In this work, slot and dipole modes corresponding to magnetic and electric currents are effectively interleaved and excited in a surface to develop a space-efficient dual-wideband aperture-shared radiating surface. In this case, due to an effective reuse of the antenna aperture over both frequency bands, a high aperture-reuse efficiency is achieved. First, we devise a planar magneto-electric (ME)-dipole-alike antenna and analyze it in both the frequency and time domain. The antenna is then studied by the characteristic mode theory and the findings are validated using full-wave simulations. The developed planar ME-dipole-alike antenna is used to realize a dual-wideband radiating surface in which electric and magnetic currents are mutually coupled and interlaced, which is excited by properly oriented and distributed sources on the antenna's surface. Eventually, a highly isolated dual-wideband prototype was developed and fabricated using a cost-effective multi-layer Printed Circuit Board (PCB) process that operates in the Ku-band with both impedance and gain bandwidth of approximately 42% and in the Ka-band with respective impedance and gain bandwidth of 29% and 16.32%. [ABSTRACT FROM AUTHOR]

Radar imaging is a technology that uses radar systems to generate target images. It transmits radio waves, receives the signal reflected back by the target, and realizes imaging by analyzing the target's position, shape, and motion information. The three-dimensional (3D) forward-looking imaging of missile-borne radar is a branch of radar imaging. However, owing to the limitation of antenna aperture, the imaging resolution of real aperture radar is restricted. By implementing the super-resolution techniques in array signal processing into missile-borne radar 3D forward-looking imaging, the resolution can be further improved. In this paper, a 3D forward-looking imaging algorithm based on the two-dimensional (2D) super-resolution algorithm is proposed for missile-borne planar array radars. In the proposed algorithm, a forward-looking planar array with scanning beams is considered, and each range-pulse cell in the received data is processed one by one using a 2D super-resolution method with the error function constructed according to the weighted least squares (WLS) criterion to generate a group of 2D spectra in the azimuth-pitch domain. Considering the lack of training samples, the super-resolution spectrum of each range-pulse cell is estimated via adaptive iteration processing only with one sample, i.e., the cell under process. After that, all the 2D super-resolution spectra in azimuth-pitch are accumulated according to the changes in instantaneous beam centers of the beam scanning. As is verified by simulation results, the proposed algorithm outperforms the real aperture imaging method in terms of azimuth-pitch resolution and can obtain 3D forward-looking images that are of a higher quality. [ABSTRACT FROM AUTHOR]

This paper proposes a dual-band patch antenna with combined self-decoupling and filtering properties, designed to suppress mutual coupling between two antenna elements both within the same dual-band and across different dual-bands. Initially, a dual-band aperture-coupled filtering patch antenna is designed, featuring a forked short-circuited SIR feedline with a quarter-wavelength open-ended stub and a U-shaped patch with two U-slots, which generate three controllable radiation nulls while introducing two additional resonant modes. The design steps are also provided in detail. Subsequently, the low mutual coupling phenomenon of two vertically placed aperture-coupled patch antennas is investigated, successfully developing a high-isolated dual-band two-element MIMO array I. Furthermore, the other quad-band two-element MIMO array II is designed, which utilizes the filtering response to significantly reduce mutual coupling across four bands. Finally, a dual-band filtering patch antenna element and two two-element MIMO arrays are fabricated and measured. The measurements and simulations validate the antenna's low mutual coupling performance in multi-band MIMO arrays and demonstrate its strong potential for future wireless communication applications. [ABSTRACT FROM AUTHOR]

A compact dual-band circularly polarized (CP) shared-aperture antenna is proposed for satellite communication. The antenna enables simultaneous dual-band functionality and CP radiation with right-handed CP in the Ku band and left-handed CP (LHCP) in the Ka band. The shared-aperture is implemented by integrating two independent subapertures, which function through frequency-multiplexed, resulting in a minimized profile (0.04 $ {\lambda _0} $ λ 0 ) and reduced complexity, making it an ideal choice for array applications. To enhance inter-frequency isolation, a circular arrangement of metal vias is incorporated. The measured results indicate that the antenna effectively encompasses a 3 dB axial ratio (AR) bandwidth of 15.6–16.5 GHz in Ku and 26.5–27.5 GHz in Ka bands. Additionally, it exhibits a broader 10 dB impedance bandwidth (IBW) and superior port isolation bandwidth exceeding 30 dB. [ABSTRACT FROM AUTHOR]

We demonstrate the generation of highly directive circularly polarized beams by proposing a meta-lens to calibrate the near fields over the holographic surface. Such a design possesses the merits of ultra-low profile as a lens system on the basis of phase compensation of a specific radiating aperture rather than the conventional consideration of the lens focus, and the ratio between the overall height of the antenna architecture and diameter of radiating aperture is only 0.09. Especially, the proposed meta-lens integrated holographic surface also offers a satisfactory solution to improve the overall efficiency of holographic antennas, and the experimental results verify the proposed design with 27.6 dBic measured gain and 40.4 % aperture efficiency at 15 GHz. We expect the proposed strategy of integrating phase compensation lens closely over the holographic surface, pave the way for highly efficient meta-radiators with ultra-low profile. [ABSTRACT FROM AUTHOR]

Angle estimation for low-altitude targets above the sea surface is a challenging problem due to multipath interference from surface reflection signals, and various approaches have been proposed. This paper proposes a matrix pencil method with multiple apertures. The matrix pencil method effectively responds to dynamic scenarios because it performs better when using a single snapshot than other methods. Also, employing multiple apertures is more economical than using one large aperture. Therefore, we propose a computationally efficient approach using this method and structures. The proposed two-stage MP method incrementally improves the resolution in two stages: in stage 1, we extract the denoised signals at each aperture level, and in stage 2, we further improve the resolution with those signals. In comparison with the angular resolution defined by the half-power beamwidth (HPBW) of a uniform linear array (ULA) antenna with an equivalent number of arrays, the proposed method demonstrated a superior resolution of less than 0.087 of the HPBW at a high signal-to-noise ratio (SNR) of 40 dB, and less than 0.31 of it even at a relatively low SNR of 15 dB, based on 90% of the resolving probability. For the multipath problem, the proposed scheme has the advantage of not requiring prior geometric information, and its performance is demonstrated through simulations to be better than the adaptive beamforming method and the composite monopulse method. [ABSTRACT FROM AUTHOR]

This paper proposes a novel feed array antenna to achieve a uniform electric field distribution in the near-field region for feeding a large-aperture antenna. The feed antenna has a 4 × 4 rectangular array configuration to obtain uniform near-field distribution on a virtual target surface. Each element of the array consists of a Vivaldi radiator and parasitic rings, and these two components have different radiating modes. In particular, the near-field pattern of the parasitic rings can be varied by adjusting their radii. Thus, the required near-field distribution on the virtual target surface can be achieved by optimizing the radii of the parasitic rings. To further enhance the uniformity of the electric field, the input phase of each Vivaldi radiator is adjusted by applying different transmission line lengths to the Vivaldi radiators depending on their positions in the array. To verify the feasibility of the proposed antenna, the electric field distributions are measured in an electromagnetic anechoic chamber. The results demonstrate that the proposed feed array antenna can achieve uniform near-field distribution with an average of 1.7 dB and a deviation of 6.8 dB on the virtual target surface placed within half a wavelength from the antenna aperture. [ABSTRACT FROM AUTHOR]

A novel probe fed right hand circularly polarized (RHCP) shared aperture antenna with concentric configuration is designed for L5 and S-bands NavIC receiver application. The structure consists of a square loop-type patch antenna for the L5 band, serves as the top radiator, and a concentrically truncated corner patch antenna for the S-band is embedded in the non-radiating portion of the L5 band antenna. The square loop is orthogonally fed with electromagnetically coupled strips with equal power and quadrature phased shift through symmetric vias. These vias are connected to the feeding network, which consists of a Wilkinson power divider that is designed on opposite sides of the ground to mitigate spurious radiations. Furthermore, the S-band antenna, placed inside the L5 band substrate, achieves CP by corner truncation. This technique increases the aperture reuse efficiency and improves the isolation between both radiators. The overall profile of the antenna is 75×75×8mm3 and exhibits a wide impedance bandwidth of 25.5% for the L5 band and 6.5% for the S-band, with an isolation of better than 20dB for both bands. The axial ratio bandwidth achieved is 25.5% and 4.1% for the L5 and S bands, respectively, with boresight gain of 3.57 dBiC and 4.8 dBiC in the L5 band and S-band, respectively. The proposed antenna is based on a shared aperture technique, which has different feeding ports for both bands; thus, it improves the G/T performance and noise figure of the overall system. These characteristics make the proposed antenna suitable for use in NavIC application. [ABSTRACT FROM AUTHOR]

Industrial radar applications like tank level measurement is an important research and application area in radar technology. Radar level measurement is a safe solution even under extreme process conditions (pressure, temperature) and vapors. Special antennas are required to meet electromagnetic requirements such as high gain, low sidelobe level and high bandwidth. The small side-beam level and narrow main beam primarily minimize reflections from the side of the tank, while the bandwidth determines the distance resolution of the measurement system. Another requirement is a small size and good manufacturability of the antenna. The main promising solutions are the use of microstrip, horn or dielectric lens antennas for tank level measurement systems. After several tests, we have concluded that the optimal choice for tank level radar measurement task, in terms of integrability and antenna parameters, is a dielectric antenna. The dielectric antenna has many other applications in modern mobile systems as 5 and 6 G systems where these antennas are elements of antenna arrays of beamforming or MIMO systems. In this paper, a special dielectric lens antenna is presented, satisfying main requirements, namely a circular antenna cross section, high antenna aperture efficiency and low sidelobe level. The center frequency of the antenna is 26 GHz with a bandwidth of 1 GHz. The paper presents the analytic investigation and design of the dielectric lens antenna and the circular waveguide transition in detail. The electromagnetic design of the antenna was carried out using CST Microwave Studio 3D software. [ABSTRACT FROM AUTHOR]

In the present work an analytical formulation to synthesize non-uniform phase distributions at cylindrical apertures is described. Assuming three distinct amplitude distributions, the respective phases are established to provide cosecant-squared radiation patterns. Non-uniform amplitude distributions are investigated and adopted to reduce sidelobe levels and unwanted ripples in the synthesized radiation patterns. Analytical results for the established amplitude and phase distributions at cylindrical apertures are presented. The radiation patterns for such distributions are obtained by aperture method analysis, successfully demonstrating the usefulness of the new analytical formulation. [ABSTRACT FROM AUTHOR]

Abstract A dual‐band shared‐aperture antenna array is presented, involving a combined scheme to suppress mutual coupling interference. The proposed array is comprised of a low‐band (LB) antenna, a frequency selective surface (FSS), sixteen high‐band (HB) antennas, and a reflector. The LB antenna utilises electromagnetic transparent (ET) characteristics to minimise scattering interference, while the FSS isolates resonance interference and port signal interference. The combined scheme integrates the benefits of both the ET antenna and FSS to suppress mutual coupling interference effectively. A prototype of the proposed antenna was fabricated and measured, operating at 1.7–2.7 GHz and 3.3–3.9 GHz. The simulated and measured results demonstrate stable patterns for both the LB antenna and the HB antennas. The cross‐band isolation is higher than 28 dB in the low‐band. With these advantages, the antenna array is suitable for base station applications.

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In this article a compact sinusoidal tapered slot Vivaldi linear antenna array is designed for X and Ku band applications is presented. Printed Vivaldi antennas are extensively used for broadband applications because it gives high gain and broad bandwidth. The proposed antenna consists of two circular stubs, one rectangular slot and sinusoidal tapered lines on both sides of the antenna structure. These two tapered lines separated by circular slots and rectangular slot. The bandwidth of the antenna is improved with two circular stubs before the tapering. A rectangular slot is included before the two stubs to reduce the aperture width of the antenna. The feed line is then terminated with sectorial stub to have better coupling to the slot. The profile of the tapering of slot is designed as sinusoidal variation to have good end fire radiation for the entire frequency range. The simulated single antenna has return loss less than− 10 dB in between the frequencies 8.2–20 GHz. A five-element linear array is designed, simulated and prototype model is fabricated. The simulated and experimental results show return loss is less than − 7.5 dB for the frequency range of 8.2–20 GHz. The maximum gain of single element and array is 4.6 dBi and 7 dBi respectively. The Co and cross polarization radiation patterns are measured. The designed Vivaldi antenna array is used in X, KU band, electronic warfare and phased array applications. [ABSTRACT FROM AUTHOR]

In order to increase the radiation performance of aperture-type antennas, this paper demonstrates a low-profile, planar, single-layer, three-dimensional (3-D) printable metastructure. The proposed hybridized metastructure is highly transparent as it is made out of novel hybrid meta-atoms having transmission coefficient magnitudes greater than – 0.72 dB and fully complies with the near-field phase transformation principle. The hybridized design approach makes the metastructure planar, low-profile, light in weight, and compatible with additive printing technology. For the proof-of-concept, such metastructure is developed and numerically verified to enhance the radiation performance of a resonant cavity antenna (RCA). With the proposed metastructure, the peak directivity of the RCA is improved by 8.6 dBi (from 11.4 dBi to 20 dBi) at the operating frequency of 12.4 GHz. The aperture efficiency and 3-dB directivity bandwidth of the RCA with the metastructure are 41.46% and 16.5%, respectively. Using readily accessible thermoplastics or polymers and copper with cost-effective fused deposition modeling (FDM) 3-D printing technology, the proposed planar hybridized metastructure can be prototyped commercially. [ABSTRACT FROM AUTHOR]

A tri-band shared-aperture antenna for Sub-6 GHz/millimeter-wave (mmWave) applications with a scanning beam is proposed. Using structural multiplexing, the dual-band Sub-6 GHz mesh patch antenna and the millimeter-wave (mmWave) Fabry-Perot cavity antenna (FPCA) share the same radiating aperture. The metal mesh patch acts as both the radiator of the dual-band mesh patch antenna and the partial reflective surface (PRS) of the FPCA. The mechanism of the FPCA is analyzed using the ray tracing method. With the designed single-layer PRS, the proposed antenna features a scanning beam in the mmWave band without the need for tuning elements and feeding networks. An aperture-coupled patch antenna is designed as the feed source for the FPCA. Additionally, by optimally shaping the metal mesh, the patch antenna generates dual-band resonances. The antenna prototype is fabricated and measured. Measured results show that the impedance bandwidth of the antenna is 2.07% (2.39 − 2.44 GHz), 24.79% (3.18 − 4.08 GHz), and 28.42% (24.90 − 33.15 GHz), respectively. The tri-band peak gains are 8.18 dBi, 8.39 dBi, and 17.41 dBi, respectively. The beam scans from 2° to 39° in the frequency range of 25 − 33 GHz. [ABSTRACT FROM AUTHOR]

Lightning protection is important for weather radars to prevent critical damage or outages, but this can have negative effects on data quality. The existing lightning protection of the German Meteorological Service (Deutscher Wetterdienst, DWD) polarimetric C-band weather radar network consists of four vertical poles with a maximum diameter of 10 cm. During radar operation, these rods cause local scattering in the near field of the antenna, resulting in negative impacts on radar products. One effect is the removal of significant transmission power from the main beam axis and its addition to other areas or the side lobes. This results in wrongly localised precipitation fields in a radial direction. The second effect is the loss of transmitted and received power, appearing as a decrease in system gain, and subsequently an underestimation of all power-based radar moments in the vicinity of the rods. The underestimation in radar reflectivity Z then leads to a negative bias of approximately 20 % in the actual rain rate if a Z – R relationship is applied. These detrimental effects on data quality led to the requirement of developing a new lightning protection concept. The new concept must minimise the effect on data quality but also provide sufficient protection from lightning strikes according to the existing regulations and requirements. Three possible lighting protection concepts are described in this paper: two using vertical rods of different diameters (16 and 40 mm) and one with horizontally placed rods outside the antenna aperture. Their possible influence on data quality is quantified through a dedicated measurement campaign by analysing resulting antenna patterns and precipitation sum products. Antenna patterns are analysed with respect to the side-lobe levels compared to antenna patterns without lightning protection and the original lightning protection. With the newly tested lightning rods, the apparent side-lobe levels are slightly increased compared to an antenna pattern taken without lightning protection but are within the accepted antenna specifications. Compared to the original lightning protection, a decrease of up to - 15 dB in apparent side-lobe levels is found for all tested lightning protection options. Beam blockage is substantially reduced compared to the existing lightning protection, as shown by the evaluation of quantitative precipitation estimation (QPE) sums. These results and some structural considerations are a solid basis to recommend the installation of four rods with a maximum 40 mm diameter for all 17 radar systems of the DWD weather radar network. [ABSTRACT FROM AUTHOR]

This comprehensive article explores the massive MIMO (M-MIMO) design and its associated concepts, focusing on the seamless integration requirements for Beyond 5G (B5G) and 6G networks. Addressing critical aspects such as RF chain reduction, pilot contamination, cell-free MIMO, and security considerations, this article delves into the intricacies of M-MIMO in the evolving landscape of B5G. Moreover, the emerging MIMO concepts in this article include AI-enabled M-MIMO three-dimensional beamforming, reconfigurable intelligent surfaces, visible light communication, and THz spectrum utilization. This review highlights the challenges and open research issues, including Narrow Aperture Antenna Nodes, Plasmonic Antenna Arrays, Integrated Sensing with M-MIMO, and the application of federated learning in M-MIMO systems. By examining these cutting-edge developments, this article aims to advance knowledge in the field and inspire future research directions in the exciting realm of B5G and 6G networks. [ABSTRACT FROM AUTHOR]

A novel metamaterial-element based frequency selective surface (FSS) is proposed in this paper for multiband radome for airborne application, which exhibits angular stability and polarization independence up to incidence angle, 60°C. The proposed metasurface radome consists of a combination of different patch-type elements in two cascaded layers, forming an electrically thin design suitable for aerospace applications. It operates in the frequency bands, S- (3.3 GHz), C- (4.8 GHz), and X- (9.1 GHz) with high transmission efficiency and good isolation between bands (< -20 dB). An equivalent circuit model of the proposed design is derived and validated with the simulated (based on HFSS) and measured results. Further, a multilayered planar laminate is designed using the proposed metamaterial-element based FSS that exhibits transmission bandwidths, 220 MHz, 1 GHz, and 1.3 GHz corresponding to S-, C-, and Xbands, respectively, w.r.t-1 dB insertion loss. The structural analysis of multilayered radome wall configuration confirms its suitability for shared aperture antenna integrated to leading wing structure of aircraft. [ABSTRACT FROM AUTHOR]

A dual‐band shared‐aperture antenna array is presented, involving a combined scheme to suppress mutual coupling interference. The proposed array is comprised of a low‐band (LB) antenna, a frequency selective surface (FSS), sixteen high‐band (HB) antennas, and a reflector. The LB antenna utilises electromagnetic transparent (ET) characteristics to minimise scattering interference, while the FSS isolates resonance interference and port signal interference. The combined scheme integrates the benefits of both the ET antenna and FSS to suppress mutual coupling interference effectively. A prototype of the proposed antenna was fabricated and measured, operating at 1.7–2.7 GHz and 3.3–3.9 GHz. The simulated and measured results demonstrate stable patterns for both the LB antenna and the HB antennas. The cross‐band isolation is higher than 28 dB in the low‐band. With these advantages, the antenna array is suitable for base station applications. [ABSTRACT FROM AUTHOR]

Communication systems need antennas with wide bandwidths to provide large throughput, while imaging radars benefit from high gain for increased range and wide bandwidths for high-resolution imaging. This paper presents the design and evaluation of a wideband, high-gain antenna that achieves an average gain of 9.7 dBi over a bandwidth of 1.49 GHz to 3.92 GHz by using multiple in-phase radiating apertures. The antenna has a unique structure with a central rectangular short-circuited patch sandwiched between two back-to-back U-shaped radiating patches and two flanking H-shaped short-circuited patches. Each of the U-shaped patches employs a coplanar waveguide as feeding to achieve ultra-wideband impedance matching. Benefiting from design arrangement, in-phase electrical field distributions appear at the gaps between the patches that result in equivalent radiating magnetic currents in the same direction. Theory analysis shows that the close-spaced, same-direction magnetic currents created by the radiating apertures intensify the radiation and increase antenna gain within its impedance bandwidth. Simulated data show that the use of the coplanar waveguide feeding and short-circuited patches increase the bandwidth from 65 MHz to 2.43 GHz. Moreover, the short-circuited patches increase the gain by 3.45 dB at 2.4 GHz. Simulation and measurement results validate the design and show that the antenna features a maximum gain of 11.3 dBi and an average gain of 9.7 dBi in a fractional bandwidth of 89.8%. Because of the high gain values and the wide bandwidth, the antenna is particularly suited for long-range communication systems and high-resolution radar applications. [ABSTRACT FROM AUTHOR]

In this paper, authors propose a new way of improving the gain-bandwidth performance of Ultra-Wideband (UWB) antenna using annular ring arcs. Annular ring arc is portion of the annular ring with specific length and sector angle that contributes to effective aperture area of the antenna. Hence, such structure helps to improve gainbandwidth performance of antenna. Length, width, and angle of ring-arc was calculated mathematically based on effective aperture of antenna. Placement of annular rings is another important factor discussed in this paper that was found by experimentation. The antenna design is finished within three iterations and finalized antenna was fabricated and tested. Measurement results and simulation results of antenna agreed. The antenna frequency band ranges from 2.1 GHz to 10.4 GHz with achieved size reduction of 38.74%. The antenna was fabricated on FR4 epoxy substrate with 0.8 mm thickness and dielectric constant of 4.4 and achieves acceptable return loss over the band of operation. [ABSTRACT FROM AUTHOR]

The performance of the antennas, which plays an important role in millimeter-wave astronomy and space communication, is often limited by their reflector surface accuracy. Microwave holography is a fast and effective technique for measuring the surface profile of reflector antenna. In this paper, the antenna aperture phase profile is obtained by microwave holography to estimate the deviation between the reflector of the Tianma 65 m radio telescope and the ideal paraboloid. The panels of the Tianma 65 m radio telescope is in radial pattern with 14 rings. Each corner of the panel is fixed on the screw of the actuator to move up and down, and the adjacent corners of the four panels share an actuator. We use the method of plane fitting to calculate the adjustment value of every panels corner. But one actuator, which simultaneously controls the common corner of the adjacent panels, will have different adjustment values according to the plane fitting equation based on adjacent panels. In this paper, an adjustment value at the corner of the adjacent panel is obtained by plane fitting and adjustment calculation method with the antenna illumination function as the weight, that is, the optimal adjustment value of 1104 actuators of the Tianma 65 m radio telescope. Through many adjustments and the application of new algorithms, the surface accuracy of the reflector of the Tianma 65 m radio telescope has gradually improved to the current 0.24 mm. [ABSTRACT FROM AUTHOR]

A wideband shared-aperture antenna is designed for MIMO application based on asymmetric orthogonal-mode antenna pair. A symmetric T-shaped antenna and an asymmetric double-L-shaped antenna constitute the proposed antenna pair. Two co-planar antenna elements are configured above the ground (on the same substrate side). The wideband self-decoupling characteristic of the antenna pair is achieved via orthogonal modes. The proposed shared-aperture antenna demonstrates good impedance matching, high isolation, and good diversity performance over a bandwidth of 3.04–5.28 GHz, covering the 5G N77/N78/N79 bands, which is suitable for compact 5G MIMO terminals. Two such antenna pairs are arranged along the upper side of the ground to construct a 4-port MIMO antenna. The proposed MIMO antenna is fabricated and tested to verify its performance. Favorable results are realized, including impedance matching, isolation, efficiency, and ECC. The measured results are in good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

There are deviations between the radio telescope antenna finite element (FE) model, founded on the design stage, and the actual working antenna structure. The original FE model cannot accurately describe the antenna structure deformation characteristics under the environmental load, thereby compromising the accuracy of the active structural compensation. This article proposes an antenna FE model updating method founded on parameter optimization with a surrogate model. The updating method updates the modulus of elasticity parameters of different components of the antenna backup structure (BUS) to obtain finite element analysis (FEA) results consistent with the actual measurement of the antenna reflector surface shape. The surrogate model founded on the multi-quadratic radial basis function (RBF) improves the computational efficiency of FE model updating, replacing the complex and time-consuming finite element analysis and calculation process. This method is implemented on a radio telescope antenna with an aperture of 25 m. The results show a significant reduction in the mismatch between the antenna and the updated FE model. This method's calculation time is significantly reduced compared with the updating method without using the surrogate model, with the RBF surrogate model taking 1% of the time of the finite element model in the FEA calculations. The proposed method can improve the antenna FE model calculation accuracy and significantly enhance the efficiency of FE model updating calculations. Thus, it can offer a reference for antenna engineering practice. [ABSTRACT FROM AUTHOR]

The accuracy of the pointing error in the subreflector is of great importance to the large steerable radio telescope, so the measurement of the six degree-of- freedom (DOF) poses of the subreflector is crucial, which are measured by the detector and the laser array. The errors in the pose measurement system of the subreflector contain random measure errors and fitting iteration errors; all of them will add up to the pose measurement, which affects the accuracy of the six DOF parameters. This paper proposed the accuracy analysis method in the pose measurement of the subreflector of large antennas, which includes the error in the variable model in laser three-dimensional point space linear fitting, iterative accuracy analysis of spatial equations in Newton's downhill method, and the analysis of the adjustment theory of the Bursa model. The experimental results show that the measure time in six-DOF poses of the subreflector in a large- aperture antenna is at most 0.5 s, while the measurement accuracy error of translation is within 0.0131 mm and the error of rotation is within 0.2323°, which indicates that the pose measurement method of the subreflector in large antennas based on stereo structured light is efficient and applicable enough to analyze the measurement system accuracy. [ABSTRACT FROM AUTHOR]

In the design of horn array antennas, usually there is a challenge with the grating lobe problem and consequently quite low aperture efficiency. A new configuration for horn array antennas is presented which introduces high aperture efficiency with suppressed grating lobes in both E‐& H‐plane radiation patterns. The proposed array unit cell is a dual‐mode horn loaded by two corrugations in E‐plane. A sample 4 ⨯ 4 array of the proposed unit cell is designed to operate at Ku band. The simulation and measurement results show 13.3% operating bandwidth over which the grating lobes are totally suppressed and the aperture efficiency is above 70%. The antenna measured gain is also 27 dBi with 2 dB variation over the bandwidth. The results show that the aperture efficiency of 98% is achievable making use of the proposed topology. [ABSTRACT FROM AUTHOR]

Summary: The investigations related to the planar antenna array have attracted much attention due to their vast applications in the areas of advanced wireless communication and electromagnetics. This article presents an effective synthesis method of a sparsely thinned symmetric planar antenna array using three well‐known meta‐heuristics including symbiotic organism search (SOS) algorithm, moth fly optimization (MFO), and multi‐verse optimization (MVO) algorithms. The main aim of this work is to optimize the positions of the switched‐on antenna elements on the array aperture in order to reduce the value of side‐lobe levels in the radiation field pattern in multiple planes for a desired first null beam width and subsequently to obtain the maximum reduced number of array‐elements in the antenna array. Two different cases are performed to optimize the radiation pattern in different azimuth angles with two different examples. The proposed methods can constrain the total number of array elements, inter‐element distance, and aperture area of the array. The radiation pattern characteristic and computation time linked with each example and each algorithm are recorded and compared with each other as well as with a fully populated planar symmetric rectangular array antenna of same aperture size for arriving at the conclusion. The simulation‐based results demonstrate the effectiveness of the proposed design and the efficiency of the performance using the SOS algorithm. [ABSTRACT FROM AUTHOR]

A novel dual band tunable terahertz (THz) circularly polarized dielectric resonator antenna (CPDRA) is designed and numerically studied. Hybrid Silicon-Graphene materials are employed as radiator with cross-slot shaped aperture coupled feed, enabling tunable linearly and circularly polarized radiation. Silicon is a good material as dielectric resonator with its operation in the THz regime due to lack of absorption, cheaper to grow and machine. Cross shaped slots of appropriate dimensions are engraved in the centre of the ground plane to split the fundamental mode of the rectangular DR into two near degenerate orthogonal modes having quadrature phase difference. As a result, circular polarization is obtained in the upper passband. Introducing cross slot also helped to improve the impedance matching and dual band operation is achieved with linearly polarized response in lower band and circularly polarized response in the upper band. By adjusting the chemical potential of graphene, frequency tunability in the both the operating bands is obtained, without changing the physical geometry of the antenna. The proposed antenna operates with 10 dB impedance bandwidth of 4.24 \% (2.31–2.41 THz) and 12.1 \% (3.11–3.51 THz) and 3 dB axial ratio bandwidth of 3.54 \% (3.33–3.45 THz). The antenna parameters are calculated and gain of 6.11 dBi and 5.8 dBiC in lower and upper band, respectively and radiation efficiency of 96.5 \% in both operating bands is obtained. This hybrid radiator-based THz CPDRA shows great potential in the development of tunable THz devices and could pave a path for new researchers. [ABSTRACT FROM AUTHOR]

This article presents a dual‐band shared aperture antenna array designed for ASAR applications. The antenna array comprises eight elements for Chebyshev array configurations in both X/Ku‐bands. The proposed array achieves a scanning angle of ±25° by employing an interelement spacing of 0.7 λ. The layout mitigates mutual coupling effects and provides good isolation performance between the X‐ and Ku‐band antenna arrays across all synthesis techniques. Adopting the open, short, and load antenna array achieves different side lobe level (SLL) performances, >−25 dB. The isolation between bands and between the three conditions is quantified as follows: S16 = S61 = −68 dB, S15 = S51 = −55 dB, S12 = S21 = −46 dB, S43 = S34 = −49 dB, and S56 = S65 = −43 dB. The SLL values for each synthesis technique in the X/Ku‐band are as follows: Chebyshev simulated and measured results for open‐ended (X/Ku‐band: −26/−24 dB/−27/−26.8 dB). Furthermore, the antenna array achieves maximum realized gains in different positions (0°, 5°, 10°, 15°, 20°, 25°) in the X/Ku‐band. The gains for each synthesis technique are as follows: Chebyshev (The measured gain of this X/Ku‐band is high around 16.2/16.5 dBi (open‐ended), 13.1/14.2 dBi (short‐ended), and 15.3/15.2 dBi (load‐ended). The antenna array exhibits a comparatively wide impedance bandwidth Chebyshev (X/Ku‐band: 100/230 MHz). [ABSTRACT FROM AUTHOR]

This research looks at microwave devices, specifically, patch antenna along with electromagnetic spectrum, shape, mechanism, analytical methods, simulation tools, and feeding procedures. Patch antennas are distinguished by their rectangular form, with a patch on one side and a ground plane on the other. Patch antennas work by exciting electromagnetic waves inside the patch, which are subsequently transmitted into the surrounding environment. The report also outlines numerous ways for evaluating the performance of microstrip patch antennas. The electromagnetic characteristics of the antenna are analyzed using the transmission line model, cavity model, and multiport network model (MNM). The integral equations that regulate the behavior of the antenna are solved using the method of moments (MoM) and the finite element method (FEM). The spectral domain technique (SDT) is used to analyze the antenna’s frequency response, while the finite difference time domain (FDTD) approach is used to analyze the antenna’s time-domain behavior. Overall, these methodologies give a thorough understanding of microstrip patch antenna performance and may be utilized to optimize their design. Furthermore, several patch antenna feeding methods, such as probe feed, microstrip line feeding, aperture coupling, proximity coupling, and CPW feed, are investigated. Attaching a microstrip line to the patch, which is subsequently linked to the RF source, is what microstrip line feeding entails. Aperture coupling entails making a hole in the ground plane that allows the RF source to feed the patch directly. Proximity coupling is accomplished by placing a probe near the patch, which creates an electromagnetic field on the patch. Patch antenna simulation software includes programmers such as HFSS, CST, and FEKO. These tools simulate the patch antenna’s performance, including its radiation pattern, gain, and input impedance. These simulations may be used to optimize the patch antenna design for specific applications. Moreover, recent antenna trends are presented in this article. [ABSTRACT FROM AUTHOR]

We report on the theoretical design and experimental verification of a high efficiency microwave wireless power transmission (MWPT) system operating in the Fresnel region. To achieve high conversion efficiency over a transmit distance of 11 meters, the transmit reflector antenna was optimized to locate the focal point at 11 m. The size of the receive antenna was decided by calculating the field distribution and the received power at different positions in the receive antenna aperture. Furthermore, an accurate model of the diode is presented, which was imported into the ADS software for high-precision rectifying circuit design. As a result, an overall DC-DC conversion efficiency of 20% was achieved, as measured in an anechoic chamber at a given distance of 11 m. The experimental results validated the proposed method. [ABSTRACT FROM AUTHOR]

Silicon‐based packaging is highly suitable for miniaturised and cost‐effective integrated systems. However, traditional silicon‐based antenna‐in‐package (AiP) has disadvantages, such as high loss, low efficiency and narrow bandwidth. A glass‐silicon active package system architecture is proposed. Its active part is integrated on a silicon substrate, while the antenna array in the package system is made of glass, which has high radiation efficiency. The proposed antenna structure is an H‐type aperture‐coupled microstrip patch antenna. The authors use a ball grid array to form cavity and two shielding structures to improve the scanning performance of the array. Furthermore, by adding grounding points, the resonance singularity within the shielding structure is eliminated. A test array, composed of 8 × 8 elements was fabricated for the purpose of validating the design. It can achieve wide‐angle scanning greater than ±60° and bandwidth of 29%. This design can be applied for ka‐band communications and radar systems. [ABSTRACT FROM AUTHOR]

In view of the challenges and difficulties encountered in the analysis and application of timedriven ultra-wideband array antennas (TD-UWB arrays), this study investigates the pulse radiation characteristics of discretized apertures based on aperture radiation theory and space superposition principle. The impact of discretized aperture linear arrays and planar arrays to restore the radiation of original aperture is examined, along with an analysis of how discretization methods influence the radiated pulse waveforms. The potential application of discretized aperture radiation in research of TD-UWB array antennas is studied, and a method is proposed for predicting time-domain radiation characteristics of TD-UWB arrays. Numerical results demonstrate that the proposed method derived from the discretized aperture radiation can effectively predict the temporal pattern and radiation waveforms of TD-UWB arrays. The research expands and advances the practical applications of aperture radiation, thereby offering a novel perspective for analyzing the radiation characteristics of TD-UWB arrays. [ABSTRACT FROM AUTHOR]

This article proposes a new design of a circularly polarized (CP) aperture antenna based on a dual‐mode rectangular waveguide cavity‐resonator. A capacitive iris is employed to attain a strong coupling between the cavity and the input port, resulting in a larger fractional bandwidth (FBW) than a conventional aperture antenna. Another capacitive iris is embedded at the corner of the radiating aperture and extended into the cavity to maintain equal amplitude and a phase difference of 90° between the radiated electric (E) fields of the TE101 and TE110 modes, and thus yielding CP radiation. The proposed antenna has been fabricated using a computer numerical control machine. The antenna has an FBW of 18% at center frequency (f0) f0 = 10 GHz when the reflection coefficient (S11) S11 = −10 dB. The 3‐dB axial ratio bandwidth is 7%. A gain of 8.0 dBic is found at 10.06 GHz. The low profile and competitive performance of the antenna make it a good candidate in radar applications. [ABSTRACT FROM AUTHOR]

A novel reflect‐transmit‐array antenna is proposed in this paper, in which a single‐layer heteropolarized element with a thickness of 0.1 λ0 ${\lambda }_{0}$ at 11 GHz, consisting of only two layers of metal patches printed on a dielectric substrate and six metal vias, can integrate reflection and transmission modes in the same frequency band by reasonably distributing the positions of the reflection and transmission parts in the element. We designed, fabricated, and measured the reflect‐transmit‐array antenna with an aperture of 501.2 mm2. At 11 GHz, the maximum gain of reflection is 17.7 dB, and the peak gain of transmission is 20.4 dB, indicating that this scheme has good application prospects in bidirectional wireless communication. [ABSTRACT FROM AUTHOR]

A novel aperture‐shared dual‐wideband 5G antenna with dual polarization in the sub‐6 GHz band and multi‐input multi‐output (MIMO) function in the 28‐GHz band is presented in this work. A dual‐polarized megnetoelectric dipole (ME‐dipole) with wide bandwidth is introduced in the sub‐6 GHz band. Based on the partial structure reuse method, four 2 × 2 substrate integrated waveguide (SIW) cavity‐backed patch arrays are integrated into the electric dipole structure of the ME‐dipole to construct a 28‐GHz 2 × 2 MIMO system. Two high‐order SIW cavity modes that cooperate with patch modes are used to enhance bandwidth in the 28‐GHz band. For demonstration, a prototype of the proposed antenna was fabricated and measured. The simulated results are in good agreement with the measured results, showing wide bandwidths of 39.6% and 10.85% in the sub‐6 GHz and the 28‐GHz bands, respectively. In addition, excellent measured in‐band and cross‐band isolations of over 44.4 dB and 45.2 dB are obtained, respectively. [ABSTRACT FROM AUTHOR]

With the increase of antenna aperture and frequency, the influence of solar heat on its performance becomes more and more serious. In this paper, the thermal model of the 110 m aperture radio telescope to be built in Xinjiang is established to study its temperature field characteristics on the summer solstice. The results are as follows: during the day, the highest temperature of the main reflector can reach 42.86 ∘ C, which appears at 14 o'clock, and the temperature of the legs also reaches the peak of 41.74 ∘ C at the same time. The horizontal temperature difference of the back frame will exceed 1 ∘ C at 5, 18, and 19.5 o'clock, the antenna pointing performance will be greatly affected. The temperature field at night is also not uniform, and the temperature difference of the pitching structure is significantly higher than that of other components, with the maximum temperature difference of 6.42 ∘ C. Through the method of numerical simulation and test, it is proved that the wall thickness difference of components is the main reason for the large temperature difference at night. [ABSTRACT FROM AUTHOR]

In scenarios with constrained physical aperture sizes, aiming to enhance the resolution and accuracy of Direction of Arrival (DOA) estimation, this paper proposes a novel approach that integrates a moving synthetic virtual array with Sparse Bayesian Learning (SBL) for DOA estimation. Initially, a virtual array is constructed based on the motion characteristics of the target. Subsequently, the SBL method is employed to estimate the DOA of the target. Simulation experiments validate the effectiveness of this approach, demonstrating comparable DOA estimation performance to synthetic aperture methods with larger aperture sizes, even in situations with limited aperture expansion. Furthermore, under constant virtual aperture expansion, this method surpasses non‐SBL methods regarding DOA resolution. We explore the construction of a virtual array through the relative displacement induced by target motion. It further investigates the performance improvement of Direction of Arrival (DOA) estimation resolution using sparse Bayesian learning within the context of a virtual array. [ABSTRACT FROM AUTHOR]

A novel dual-band dual-polarization shared aperture antenna is proposed, which covers frequencies 1.7-2.6 GHz and 3.3-3.8 GHz. The structure, with low radar cross section (RCS), is designed to reduce the radiation interference on the high band (HB) antenna. Additionally, by introducing U-shaped slots on the arms of the low band (LB) antenna, polarization isolation between the HB elements is significantly enhanced, which can reach up to 25 dB across the whole band. Moreover, to restore the radiation pattern of the LB antenna, the dielectric substrate is employed beneath the HB antenna as a substitute for the ground plane. The antenna proposed in this paper possesses attributes of broadband, compact size, and simplified structure. [ABSTRACT FROM AUTHOR]

A compact filtering antenna with multi-adjustable radiation nulls is designed. Initially, a conventional aperture-coupled antenna is crafted by fine-tuning positions of the gap and radiation patch, achieving a radiation null. Additionally, an aperture-coupled filtering antenna is created by cascading a resonator with a microstrip feedline. Subsequently, the integration of the aperture-coupled antenna and the filtering antenna results in a dual-slot aperture cross-coupling filtering antenna, with two radiation nulls at both ends of the passband. Finally, a pair of slot lines is etched on the radiation patch, introducing an extra radiation null to enhance selectivity further. The measured results show that the proposed filtering antenna has a bandwidth from 2.44 to 2.64 GHz for |S11|<−10 dB, a peak gain of 5.5 dBi, and three radiation nulls at 2.3, 2.75, and 3.15 GHz enhancing the selectivity. [ABSTRACT FROM AUTHOR]

In this paper, low-cost methods of improving horn antennas are studied based on the recently introduced E-plane sectionalized rectangular horn antennas. In the beginning, application of E-plane sectionalizing of the rectangular horn antennas on open-boundary E-plane sectoral horn antennas is reexamined and a simple method for obtaining high gain and low sidelobe levels (SLLs) is introduced. Subsequently, effects of removing the conductive sheets from the modified E-plane sectionalized horn antenna are studied and a simple horn antenna with octagonal aperture is obtained with slightly reduced efficiency. Finally, an ultra-low-cost method of improving simple rectangular horn antennas is introduced based on this study. The purpose is to compensate the destructive effects of high SLLs of reference antennas in the antenna measurements, since a common reference antenna type is the rectangular horn antenna, which has high SLLs on the E-plane. In particular, efficiency improvement and SLL reduction of rectangular horn antennas are achieved by adding only four triangular conductive sheets to construct octagonal horn antennas. [ABSTRACT FROM AUTHOR]

The Physical Optics (PO) method is used to derive simplified expressions to compute the radiation electric fields of planar graded-index and geodesic lenses based on a parallel-plate waveguide (PPW) implementation. If the PO method is combined with ray-tracing (RT) techniques, the resulting RT-PO procedure is capable of computing radiation patterns and gain of the PPW-based lens antennas when their apertures have a general shape and the electric field is vertically polarized. The RT-PO method is validated by comparing it with the full-wave simulation results of the commercial software ANSYS HFSS for three application cases. The results show that the RT-PO approach is not only very efficient from a computational point of view but also accurate, thus being a very convenient analysis/design tool for this kind of antenna.